The problem with roll film holders is I never seem to have enough. When I want to use one it always seems to be filled with half used film stock I do not want to use. Yesterday I wanted to shoot 2x3 black and white and found those holders already filled with half used Velvia. I ended up shooting 6x7 instead but very nearly found myself reaching for 2x3 holders. Typing this now though I have had a Eureka moment. Swap the insert in the changing bag to one from a Graflex roll film holder from a larger format camera I am not currently using.